The present invention relates to an apparatus for automatic actuation of a vehicle restraint. Such vehicle restraints are used, for example, to restrain vehicles which are parked at a loading dock. The inventive actuator is intended for use with a vehicle restraint of the type disclosed in copending, commonly-assigned application No. 07/466,799, filed Jan. 18, 1990. However, the actuator is susceptible of a wide range of use with many types of vehicle restraints.
Vehicle restraints have been used in the material handling industry to prevent a vehicle from moving away from the loading dock as the vehicle is being loaded or unloaded. Such restraints are substitutes for chains and wheel chocks. All such restraints hold vehicles by holding the vehicle's ICC bar, such a bar being a requirement for vehicles which carry heavy loads. Such ICC bars, as required by law, are placed at the rear of a vehicle, within specified height and distance parameters from the ground and from the rear of the vehicle. As the vehicle is loaded and/or unloaded, it tends to "float", that is, move vertically, thereby varying the vertical position of the ICC bar from the ground.
There are a variety of vehicle restraints which have been proposed to restrain vehicles, yet take into account vehicle float. Various categories of these are described in the above-mentioned copending application. The disclosure of that application is incorporated herein by reference.
One of the deficiencies in all of the categories of vehicle restraints discussed in that application is that some action by the operator is required to actuate and release the restraint. Such operator intervention is not always advisable, because in some circumstances, for example, restraint may be activated too early, or released too soon.
There are some vehicle restraints which are activated automatically when the presence of a truck is sensed by a wand or a photo-electric eye. However, both of these approaches require electric controls and a power source to actuate the device. Further, a time delay device is required in the control circuit so that the device does not engage as soon as the truck is detected, but rather allows time to re-orient the truck if it is not parked properly.
Another type of early model vehicle restraint used a mechanical wand which sensed the presence of the truck and thus actuated the vehicle restraint. However, this mechanical approach was unacceptable because it was not possible to impose a time delay. Further, some automatic vehicle restraints are activated through an electrical circuit which senses actuation of a dock leveler. Such an approach would be attractive, because the dock leveler ordinarily will not be actuated until the truck is properly parked. However, this electrical approach requires electric controls and a power source to actuate the restraint.